Implement optional constant-time decryption flow to hinder Bleichenbacher-like
attacks against RSA- and ElGamal public-key encrypted session keys.
Changes:
- Add `config.constantTimePKCS1Decryption` to enable the constant-time
processing (defaults to `false`). The constant-time option is off by default
since it has measurable performance impact on message decryption, and it is
only helpful in specific application scenarios (more info below).
- Add `config.constantTimePKCS1DecryptionSupportedSymmetricAlgorithms`
(defaults to the AES algorithms). The set of supported ciphers is restricted by
default since the number of algorithms negatively affects performance.
Bleichenbacher-like attacks are of concern for applications where both of the
following conditions are met:
1. new/incoming messages are automatically decrypted (without user
interaction);
2. an attacker can determine how long it takes to decrypt each message (e.g.
due to decryption errors being logged remotely).
Fix RSA key generation code used when no native crypto library is available
(i.e. no NodeCrypto or WebCrypto). Now generated keys are always of exact bit
length. This was not guaranteed before, and it was common for keys to be one
bit shorter than expected.
Also, remove leftover code related to legacy WebCrypto interfaces (for IE11 and
Safari 10).
- Use PascalCase for classes, with uppercase acronyms.
- Use camelCase for function and variables. First word/acronym is always
lowercase, otherwise acronyms are uppercase.
Also, make the packet classes' `tag` properties `static`.
Refactor functions to take the configuration as a parameter.
This allows setting a config option for a single function call, whereas
setting `openpgp.config` could lead to concurrency-related issues when
multiple async function calls are made at the same time.
`openpgp.config` is used as default for unset config values in top-level
functions.
`openpgp.config` is used as default config object in low-level functions
(i.e., when calling a low-level function, it may be required to pass
`{ ...openpgp.config, modifiedConfig: modifiedValue }`).
Also,
- remove `config.rsaBlinding`: blinding is now always applied to RSA decryption
- remove `config.debug`: debugging mode can be enabled by setting
`process.env.NODE_ENV = 'development'`
- remove `config.useNative`: native crypto is always used when available
- Store private and public params separately and by name in objects,
instead of as an array
- Do not keep params in MPI form, but convert them to Uint8Arrays when
generating/parsing the key
- Modify low-level crypto functions to always accept and return
Uint8Arrays instead of BigIntegers
- Move PKCS1 padding to lower level functions
In the lightweight build, lazily load bn.js only when necessary.
Also, use Uint8Arrays instead of strings in PKCS1 padding functions, and
check that the leading zero is present when decoding EME-PKCS1 padding.
Also, when generating RSA keys in JS, generate them with p < q, as per
the spec.
Also, when generating RSA keys using Web Crypto or Node crypto, swap the
generated p and q around, so that will satisfy p < q in most browsers
(but not old Microsoft Edge, 50% of the time) and so that we can use the
generated u coefficient (p^-1 mod q in OpenPGP, q^-1 mod p in RFC3447).
Then, when signing and verifying, swap p and q again, so that the key
hopefully satisfies Safari's requirement that p > q, and so that we can
keep using u again.
